: I have a few suggestions on how to make it even better: the Chief will be
: accompanied by Palmer who will act as a companion NPC, much like Sgt.
: Johnson in the original trilogy, only as an exciting new dynamic Palmer
: will not be invincible. Her dying will automatically revert to last
: checkpoint, bringing a new level of urgency to the game experience.

Unlikely. Sarah Palmer is a senior officer and doesn't really need to be in the field unless a Spartan battalion is going all Thermopylae on somebody.

: On top of that the whole beloved cast of characters from the Traviss novels
: will feature. The Chief will travel aboard the Port Stanley with Serin
: Osman as his boss (during missions, she'll act much like Palmer in Spops).

Osman should definitely make a precense, but decentralization of authority needs to seep into Halo. John doesn't need to have personal access to an Admiral at his leisure. Bringing in a Lieutenant Colonel or Commander for a more localized touch would be more desirable.

: The pilot from the books will be the new Foehammer and finally seeing her
: super-upgraded Pelican in action will be sure to excite fans of the
: series. The two ODSTs will act as NPCs like Palmer on some missions, as
: will Phillips - fans will love the escort missions with him. The wacky
: intra-team banter and dynamics will bring another layer of excitement to
: the game.

I can see this happening as all canon from all of Halo's mediums are now interconnected. The only concern is what to do with Naomi. Having an old school Spartan tag alongside would probably give you a false sense of superiority.

: To sever the links to the past and show that the series is headed to an
: exciting new direction, the rest of the surviving Spartan-IIs and IIIs are
: said to have been executed in an offhand comment.

Subsequently, President Charet and Lord Hood would finally have the perfect excuse to gut ONI.

: As for new enemies, Dr. Halsey has allied with Jul M'dama and the Didact, who
: has been revived after his last encounter with the Chief. After the
: failure of the Composer, the Didact has come up with a new plan to enslave
: humanity, but she needs Halsey's help to implement it. Thus he gives her
: access to Forerunner mutation tech which she uses to create a horrifying
: army of deformed slaves ("Abominations") out of both Covenant
: and captured humans (the first missions will involve a mystery of Covenant
: forces abducting humans from remote colonies). The Abominations will
: feature in a number of classes and will have their own new weapon sandbox.

Why would we want to fight Mass Effect's Collectors and Husks again? :P

: When Halsey is confronted for the first time, it's revealed that she has also
: mutated herself, allowing the artists to really flex their creative
: imaginations: massive and heavily muscled, Halsey has become a monster not
: unlike the Didact. Boasting large tusks and a fearsome robotic arm while
: retaining her blood-stained lab coat, she will be one of the three bosses
: in the game, the other two being Jul and the Didact. The Didact also has a
: new appearance, involving more spiky parts and even more deformities
: resulting from the revigoration process.